Sash balancing mechanism



Patented Dec. 11, 1951 UNITED STATES PATENT OFFICE 'sAsn BALANCING MECHANTSM Abraham de Vries and Louis de Vries, Amsterdam, Netherlands Application November 29, 1946,- seriai 51637191528 9 Claims.- (01. 16-197) The present invention relates to an imprdve ment in an extensible spring balance that is particularly useful for balancing window sash.

It has been known for some time to balance window sash and the like with springbalances instead of the earlier sash cord and weight. Spring balances of this type generally include a spiral strip member having a gradually increasing pitch that is enclosed by a pair of coil springs, one of the springs acting as a torsion spring which exerts its reactive force onthe spiral strip, and the other acting as a tension or compression spring that is extended or compressed as the sash is raised or lowered.

Although spring balances of this type have been constructed wherein the net effective force exerted by the balance remains substantially constant in all-position's, the amount ofspace made available in window frames for the recep= tion of sash balances is so small as to require a selection of springs that are incapable of balancing heavier sash.

It has now been found that it is possible to simplify the construction and increase the load capacity of an extensible spring balance by utilizing one spring which acts simultaneously as an extensible spring, i. e., as a tension or compres sion spring, and as a torsion spring. The capacity of the spring balance of this invention can be further increased, of course,- by employing a plurality of springs, each of which is simultaneously extensible and capable of exerting a torsional force on one or more spiral members.

One advantage of the-present invention, there fore, is that it greatly simplifies the construction of spring balances by eliminating oneof the two springs hitherto deemed to be necessary.

This and other advantages, as well as the principles of the present invention will become more apparent from the following detailedde'-' scription made with reference to the accompanying drawing, it being understood however, that: the invention is not limited to either thespecific embodiments illustrate'dor to the application thereof to the balancing of window sash.

In the drawing:

Figure 1 is a view in sectional elevation of one embodiment of the extensible spring balance of this invention;.

Figure 2 isa view in partial sectional el evation of! another embodiment. of the. spring balance of this invention; and.

Figure 3 forces exerted by and within the spring. balance illustrated. in Figure I while it. is being. extended is a graphic representation of the 2 from its fully contracted position to its fully ex= tended position.

The embodiment illustrated by way of example in Figure 1 includes a pair of telescoping tube members I and 2- containing two halves 3 and 4 of a coil spring, said halves merging at point 5 where they are connected to a tube member 1 by means of a pin 6-. The tube member I is slotted at both ends 8 to receive two spiral members 9; the twists of which reverse at points I0 and which are connected with the spring at'ends H'.- V

The operationof the spring balance illustrated in" Figure I incounterbalan'cing window sash wnr now be explained with reference to" Figure 3 of the drawingwherein the ordinate axis 0 1] in dicates force in kilograms exerted in an ufiwardly direction, the abscissa 0 x represents the amount of movement of the sash in a down-- wardly direction, the positively sloping line (i represents the upward reaction force exerted by the compression of the halves 3 and 4' of the spring, the negatively sloping line 12 represents the verticalcomponent of the reaction force ex erted by the halves 3 and 4 on the'spira-l strips 9' and theline e represents the weight of the win dow sash to be balanced. I

Assuming, for the" purpose-0f illustration; that the window sash weighs 25' kilograms; that it is attached to the upper end of thetelescoping tubemember Z- and the lower end of the tube member I is attached to" the window frame,- the halves 3 and 4 of the spring may be biased to exert an upward reaction force of 15 kilograms and; to"

exert atorque or rotationalforce on the tube member 1 i.- er, they tend to unwindin a cl'ockwise direction when viewed fromabove: sothat the vertical components of the forces exerted on the spiralstrip members 9 ina direction ta resist compression or telescoping of the balance will be 10 kilograms. The total force exertedby the balance is, therefore, 25' kilograms'in a direction tending to resist compression thereof andthus effectively counterbalancing the weight of the window sash.

As the sash is lowered toward its halfwvay' position, represented in Figure 3 by X1, the com:

pressive force exerted by the spring increases- At-the same time, the tube member i rotates to wind up the until it becomes25kilograms at X1.

spring but,- due to the increase in the pitch ofthe spiral members 9 as the slots in the ends 8' of the tube member approach points to; the vertical components of forces on the spiral strips tending to extend or resist compression of the spring balance decrease until they become zero" at x, l. e., when the slots engage the spiral strips at points ill. Here again the total eflective force exerted by the balance is, therefore, 25 kilograms.

When the window sash is further lowered, the reaction force due to compression of the spring increases to a maximum of 35 kilograms. At the same time, the vertical components of the reaction forces exerted by the spring on the spiral strips 9 due to the reversal of directiona'nd decrease in the pitch of the spirals increases to l kilograms, i. e., the torsional forces on the spirals tend to contract or telescope the spring balance with a force of kilograms. As a result, the net effective force exerted by the spring balance on the window sash remains at 25 kilograms.

The embodiment illustrated by way of example in Figure 2 includes a spiral strip [2 fastened to the window frame at I 3 and IS, a slotted member H in the form of a nipple that engages the convolutions of the strip and is secured to one end of a coil spring IS, the other end of said spring being fixed against movement either directly to the frame or to the spiral strip at IS. A projection l1 fastened to the window sash at 8 rotatably engages the slotted member M.

In operation, the spring I5 is compressed and unwound as the window sash is raised and stretched and wound up as the window sash is lowered.

In a typical example, the spring i5 may be biased to exert, when the window sash at 8 is in its uppermost position, an upward force of kilograms. The vertical component of the torque exerted on the slotted member H by the spring I 5 is 10 kilograms due to the low pitch at the upper operative end of the spiral member l2. As the sash is lowered, the spring [5 is simultaneously s retched and wound up. The upward force on the slotted member I4 due tothe tension of the spring l5 will increase at a certain rate. At the same time, the vertical component of the torque exerted on the slotted member l4 by the spring and acting on the spiral member I2 will, due to the increase in the pitch of the spiral, decrease at the same rate; Thus the net resultant upward force at all times remains equal.

It is to be understood that innumerable changes and modifications such as will readily occur to those skilled in the art upon reading the description maybe made without departing from the principles of the present invention. Thus, for example, only half the spring illustrated in Figure 1 need be used. In this event, the tube 1 would be secured rotatably relative to the spiral member. All such changes and modifications are intended to be included within the scope of the invention as defined in the following claims.

We claim:

1. An extensible spring balance comprising a spiral member, a slotted member in engagement with said spiral member for rotation and longitudinal movement relative to said spiral member, and an extensible coil spring surrounding said spiral member, said spiral member and said coil spring being secured at one end against rotation and longitudinal movement relative to one another at said end and said coil spring being secured at a point remote from said secured end to said slotted member to exert simultaneously an axial force and a rotative force thereon.

2. An extensible spring balance comprising a reversely twisted spiral member, a slotted member in engagement with said spiral member for 4 rotation and longitudinal movement relative to said spiral member, and an extensible coil spring surrounding said spiral member, said spiral member and said coil spring being secured at one end against rotation and longitudinal movement relative to one another at said end and said coil spring being secured at a point remote from said secured end to said slotted member to exert simultaneously an' axial force and a rotative force thereon.

3. An extensible spring balance comprising a pair of telescoping tube members, an extensible coil spring within said telescopingv tube members, said spring comprising two oppositely wound halves, a pair of spiral members within said coil spring, one end of one of said spiral members being fixed to one end of said coil spring and one end of the other of said spiral members being fixed to the other end of said coil spring, and a slotted tube member having a slot at each end thereof for engagement with said spiral members, said slotted tube member being secured to the midpoint of said spring, said spring and said spiral members cooperating to exert a substantially uniform force tending selectively to expand and contract the combined length of the telescoping tube members.

4. An extensible spring balance comprising a pair of telescoping tube members, an extensible coil spring within said telescoping tube members, said spring comprising two oppositely wound halves, a pair of reversely twisted spiral members within said coil spring, one end of one of said spiral members being fixed to one end of said coil spring and one end of the other of said spiral members being fixed to the other end of said coil spring, and a slotted tube member having a slot at each end thereof for engagement with said spiral members, said slotted tube member being secured to the midpoint of said spring, said spring and said spiral members cooperating to exert a substantially uniform force tending selectively to expand and contract the combined length of the telescoping tube members.

5. An extensible spring balance comprising a spiral member having a unidirectional twist at one end thereof, a slotted member in engagement with said spiral member for rotation and longitudinal movement relative to said spiral member, and an extensible coil spring having a first and second end and surrounding said spiral member, the first end of said coil spring being secured to the end of said spiral member remote from the twisted end thereof against rotation and longitudinal movement of said spiral member and spring relative to one another at said first end and the second end of said coil spring being secured to said slotted member to exert simultaneously an axial force and a rotative force thereon.

6. A sash balance for a window comprising a spiral member having a unidirectional twist at one end thereof and securable at one end to a window frame against movement relative thereto, a slotted member in engagement with said spiral member for rotation and longitudinal movement relative to said spiral member, said slotted member being adapted to be carried by the sash for rotational movement only relative thereto, and an extensible coil spring having a first and second end and surrounding said spiral member, the first end of said coil spring being secured against rotational and longitudinal movement adjacent the end of said spiral member remote from. the twisted end. thereof and the second end of said coil spring being secured to the slotted member for rotational movement only relative to the sash and rotational and longitudinal movement relative to the spiral member.

7. A sash balance for a window comprising a spiral member having a unidirectional twist at one end thereof, the other end being flat, said spiral member being securable at at least one of said ends to a window frame against movement relative thereto, a slotted member in engagement with the twisted portion of the spiral member for rotation and longitudinal movement relative to the spiral member, said slotted member being adapted to be carried by the sash for rotational movement only relative thereto, and an extensible coil spring having a first and second end surrounding said spiral member, the first end of said coil spring being secured against rotational and longitudinal movement adjacent and relative to the fiat end of the spiral member and the second end of the coil spring being secured to the slotted member for rotational movement only relative to the sash and rotational and longitudinal movement relative to the spiral member.

8. An extensible spring balance comprising a spiral member; a slotted member in engagement with said spiral member, an extensible coil spring surrounding said spiral member, one end of said coil spring being immovably secured to the spiral member and the other end of the coil spring being secured, at a point remote from said secured end, to said slotted member to exert simultaneously an axial force and a rotative force thereon.

ABRAHAM n2: VRIES. LOUIS DE VRIES.

REFERENCES CITED UNITED STATES PATENTS Name Date Larson May 19, 1936 Number 

